Berlin, May 13 (IANS): Bundesliga football champions Borussia Dortmund lifted the German Cup to seal a double following a 5-2 hammering of Bayern Munich at outsold Berlin Olympia stadium.

German record champion Bayern Munich suffered the fifth consecutive loss against Dortmund following a crucial hat-rick by striker Robert Lewandowski Saturday, Xinhua reported.

Dortmund midfielder Shinji Kagawa gave his side the lead when he utilized a diagonal pass by teammate Jakub Blaszcykowski, three minutes into the match.

The Bavarians levelled the score though midfielder Arjen Robben who converted from the penalty spot in the 25th minute.

Dortmund restored their lead when defender Mats Hummels netted a penalty four minutes before break. In the dying seconds of the first half Dortmund striker Lewandowski nutmegged Bayern goalie Manuel Neuer to make it 3-1.

Polish international Lewandowski sealed his brace with 58 minutes into the match when he exploited an assist inside the box to extend the lead to 4-1. Bayern was stunned by Dortmund offensive performance but nonetheless Frenchmen Franck Ribery found the back of the net to close the gap to 2-4 for Bayern at the 75th minute.

However, Borussia Dortmund defender Lukasz Piszczek capitalized on an error by Bayern goalkeeper Manuel Neuer to assist striker Robert Lewandowski to complete his hat-trick by header nine minutes before final whistle.

Thus the German champion Dortmund wrapped their title double after 103 years to astonish the Champions League finalist and German record champion Bayern. The Bavarians will focus on the Champions League final against Chelsea next weekend to grab for the only title this season.

"It was a disastrous performance. We failed in crucial moments. If you commit such errors you cannot win," Bayern Munich coach Jupp Heynckes said.

"We clinically scored great goals. This is beyond words," Dortmund coach Juergen Klopp said.